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First, the main method of molybdenum mineral feeds are molybdenite (MoS2) and its oxidation product of the molybdenum China (MoO3), and molybdenum China iron (Fe2O3? 3MoO3? 7H2O), as well as rare molybdenum lead ore (PbMoO4) and molybdenum Tungsten-calcium ore (Ca(W, Mo)O4). The analysis system can measure molybdenite, molybdenum and iron molybdenum, and molybdenum adsorbed by limonite is also included in molybdenum. Methods Molybdenum (oxide) was leached by dilute ammonia-Na2CO3 solution, followed by leaching of Mo (including iron-molybdenum) in the iron-bound phase with HCl(1+1), and molybdenum sulfide was determined in the residue. The method is applicable to the phase analysis of Mo in general molybdenum ore and geochemical samples.
Second, the reagent preparation 10:30:5 ammonia water - sodium carbonate mixed solution: said 20gNa2CO3 dissolved in 120mL water, add 100mL ammonia water, mix. Molybdenum standard solution: Weigh 0.0750g of pure MoO3 baked at 500~525°C for 1h, dissolve in a small amount of NaOH solution, acidify with H2SO4, transfer to 1000mL volumetric flask, dilute with water to the mark, and shake. This solution contained 50 μg/mL Mo.
Third, the analysis steps (1) Determination of oxide phase molybdenum. Weigh 0.5~2g (accurate to 0.0001g) sample in 250mL conical flask, add 70mL ammonia-sodium carbonate mixed solution, plug rubber plug with 50cm long glass tube, dip in water bath for 2h (molybdenum tungsten calcium When the mine is small, it can be extended to 4h). Filter in a 100 mL solution bottle. Wash the conical flask 2~3 times with water, wash the residue 3~4 times, cool, dilute to the mark with water, and mix. Part of the test solution was dispensed into a 50 mL solution bottle, and 1 drop of phenolphthalein indicator was added, and neutralized with H2SO4 (1+1) until the solution changed from colorless to red. After cooling, add 10 mL of H2SO4 (1+1) and dilute to about 25 mL with water. Add 0.5 mL of 10 g/L CuSO4 solution, 2.5 mL of 100 g/L thiourea solution, 1.5 mL of 10 g/L ascorbic acid solution, 5 mL of 500 g/L KSCN solution, dilute to the mark with water, and mix. After 6 min, the absorbance was measured with a 1 or 2 cm absorption dish at a wavelength of 460 nm. Working curve: Take a standard solution containing 0, 20, 50, 100...250 μg Mo in a 50 mL volumetric flask, add 10 mL of H2SO4 (1+1), dilute with water to about 25 mL, and follow the sample analysis step.
(2) Measurement of iron binding phase Mo. The above insoluble residue was transferred to the original Erlenmeyer flask, 50 mL of HCl (1+1) was added, and the mixture was immersed in a boiling water bath for 15 min, removed, and filtered through a medium speed filter paper (added pulp) in a 100 mL volumetric flask. Wash the cone with HCl (2+98) for 2~3 times, wash the residue for 3~4 times, dilute to the mark with water, and mix. Part of the test solution was dispensed into a 50 mL volumetric flask, and a drop of phenolphthalein indicator was added. The solution was adjusted to a red color with a 200 g/L NaOH solution. The following is the same as (1) Determination of Mo as the iron-binding phase Mo.
(3) Determination of molybdenum sulfide phase Mo. The residue of the leaching combined phase and the filter paper are placed in a corundum crucible, carbonized on a hot plate, placed in a muffle furnace, and fired at 400 to 500 ° C for 20 min. Take out, add 5g Na2O2, mix, put in a muffle furnace, melt at 600~700 °C for 3~5min. The mixture was taken out and cooled, and immersed in 30 mL of hot water in a 250 mL beaker. The leachate is boiled in an electric furnace for 25 to 30 minutes, filtered into a 100 mL volumetric flask, and 1 drop of phenolphthalein indicator is added. The following is the same as (1) Mo is determined as Mo of the molybdenum sulfide phase.
Fourth, matters needing attention (1) When there is interference ion, you can add appropriate amount of masking agent after adjusting the acidity. For example, W can be added with 4 g of citric acid, Bi and Sb can be added with 2 g of tartaric acid, and Sn can be masked by adding 10 mL of saturated oxalic acid solution.
(2) If the Mo content exceeds the working curve, the solution can be separated and diluted with the reagent blank for colorimetric analysis.
(3) Low content of Mo can be determined by catalytic polarography.
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